In imaging applications, electronic images are generated by image generation systems such as digital video cameras and scanners. The electronic images are delivered to and reproduced by image display systems, such as television receivers, projectors, and other display devices.
However, an image generated by an image generation system generally cannot be directly displayed by an image display system without further image processing because the color spaces may not be the same for the two systems. Even when the color spaces are functionally the same, the image produced by the image generation system may be in a data format different from the data format required by the display system. This problem can be solved by converting the generated image (i.e., the image data signals received by the image display system) into an image data format that is compatible with the image data format of the color space of the display system. Such image data conversion is often referred to as data decoding, and the converted image data are often referred to as decoded image data.
A number of techniques to represent a colored image with a signaling arrangement are presently known. For example, the RGB (“red-green-blue”) color space is the signal arrangement that was originally developed for color CRTs (cathode-ray tubes). To reproduce a color image in a display device requires that the image be captured and encoded with a signaling arrangement in an image source and then be decoded and reproduced in the display device. Most of the current techniques for decoding signals representing an image in a display device are operable, however, only for positive image data during the decoding processes, which is not compatible with, and does not take advantage of, the extended color spaces of recently developed high performance display devices, such as DLP® display devices, which comprise DMD (“Digital Micrometer Device”) display elements.
Following development of the RGB color-encoding system, the YCbCr color-encoding standard was developed to provide a family of color spaces which can be stored and transmitted with greater signaling efficiency than RGB color-space signals. More recently, with a view toward providing improved color rendition in high-performance display devices that are now available, an xvYCC color encoding standard was developed and then published in January 2006 to utilize a wider color-space range than that provided by the YCbCr standard, as described further hereinbelow. Signals representing color saturation levels that were out of bounds in the YCbCr standard, particularly in guard bands at low and high video saturation levels, are permissible in the xvYCC standard. Guard bands at low and high video saturation levels were included in the YCbCr standard to protect against signal overshoot in analog signal processing circuits. In addition, colors having negative excursions from a conventional triangular color gamut, which are impermissible in the YCbCr color-encoding standard, can be encoded in the xvYCC standard.
Due to its superiority over traditional encoding schemes and standards, the xvYCC standard has rapidly become deployed in systems utilizing high performance display devices. With such growing use, it has become imperative for image display systems to be capable of decoding image signals in extended color spaces, such as that provided by the xvYCC color space, and/or be capable of handling negative color components during a decoding process.
Thus, what is needed in the art is an image signal decoding arrangement that overcomes these prior color-space limitations, including inability to handle signals representing negative color component excursions.